first let me tell you fuel additives are a must now a days. you have lower sulfur in your fuels which is a lubricant. you have injectors that run your engine, in injectors they have a spring, piston and a ball, injectors will tend to stick and cause a misfire in your engine if no additive is used. it has been more common on diesels as they really have lowered the sulfur in their fuels. not only does a good fuel additive lube they also clean out the injectors and limit valve recession and reduce carbon deposits.
as for adding moly and what not, first amsoil doesn't use moly in their oil, they have high levels of zinc. that is why most of their oils are not api certified. I agree with them that zinc doesn't cause excessive cat wear like a lot of people say. zinc is like moly, it is a barrier additive and helps reduce wear. like stated above, do oil analysis to see what is happening to your engine like stated above.
redline uses a lot of moly. I personally think it had too much myself. moly will only plates up so far they it passes by until it needs more they it replaces what it used.
I have never used amsoil myself so I can't say if they are good or not.a lot of people use amsoil but most don't use oil analysis. they use it because of what is stated on the bottle.
don't go with the oils warr but the manufacture of your car as they do all that warr on your car not the oil company. I would also use the oil analysis to show the condition of your oil. there is no reason why you can't extend your drains as long as the oil is still good as it was when you put it in.
you can go to any truck-stop and get lucas fuel additive. I have tested it and it seems to work good.
